It's this process which has scientists interested in plankton's potential to reduce the greenhouse effect.

Senior Research Scientist for the CSIRO Richard Matear has been looking into whether it's possible to stimulate the growth of plankton by infusing ocean waters with iron.

RICHARD MATEAR: That enhances the phytoplankton growth, so they grow more rapidly, and the process for instance they use carbon dioxide to form organic parts, organic molecules. And then when the phytoplankton die or get eaten by other organisms, some of that carbon gets transported deep in the ocean's interior as that organic manner rains down from the upper ocean.

TIMOTHY MCDONALD: Dr Matear says that the hope is that by stimulating plankton growth, it'll be possible to trap more carbon in the ocean and help to slow down climate change.

His research has shown that it's possible to stimulate blooms of plankton by adding iron into the ocean.

Dr Matear says the potential could even outstrip forests' ability to remove carbon from the atmosphere.

RICHARD MATEAR: The attraction of the ocean is the potential to sequester carbon is much, much greater. So the kind of studies I've done for example for the Southern Ocean, if you could drive the Southern Ocean to become nitrogen limited, you'd have the potential to increase carbon uptake by the ocean by about 160 pedagrams (phonetic) of carbon over the next hundred years. So that's a large amount.

TIMOTHY MCDONALD: While it's clear that plankton blooms can absorb carbon, it's less clear how the process would work in practice.

Some of the carbon would eventually resurface and be re-released into the atmosphere. So in order to keep the carbon underwater, more iron would have to be introduced into the ocean to generate more plankton growth.

It may have other impacts on the environment.

Tom Trull, who's an Associate Professor of Marine Biogeochemistry at the University of Tasmania, says there hasn't been enough research into the possible impacts on the marine environment.

TOM TRULL: There are unknown risks, as I said earlier. We don't know how to manipulate ocean ecosystems. It could turn out that doing something like this is the equivalent of bringing rabbits into Australia, where we have some unknown and unwanted effect.

We don't have evidence for that now, but we don't have tests that it isn't likely. And proceeding to large-scale fertilisation without tests of possible negative outcomes seems premature.

TIMOTHY MCDONALD: Professor Trull says he's particularly worried about the impact it could have on coastal regions, where the process cold deplete oxygen from the water.

TOM TRULL: These schemes in terms of avoiding risk depend on the fact that we would keep the fertilisation in the phytoplankton growth in the open ocean and away from the coast, because if these induced algal blooms were to impact on coastal zones then the matter that sinks accumulates in the near surface and over a small range of depths and can cause anoxia.

TIMOTHY MCDONALD: Dr Matear and Professor Trull say more research needs to be done, but they agree that there is great potential for plankton to help combat climate change.